Microchimerism in women with recurrent miscarriage

Peripheral blood natural killer cell cytotoxicity in recurrent miscarriage: a systematic review and meta-analysis

Dysregulated natural killer (NK) cells have been associated with recurrent miscarriages (RM). Studies have suggested that high peripheral blood NK cell cytotoxicities (pNKCs) are associated with an increased risk of RM. The aim of this systematic review (SR) and meta-analysis (MAs) is to investigate the difference in pNKC between nonpregnant and pregnant women with RM and controls and determine whether pNKC is reduced by immunotherapy. We searched the PubMed/Medline, Embase, and Web of Science databases. The MAs were conducted to compare pNKCs between women with and without RM before and during pregnancy as well as pre- and post-immunotherapy. Risk of bias in nonrandomized studies was assessed by the Newcastle-Ottawa Scale. Statistical analysis was performed using the Review Manager software. A total of 19 studies were included in the SR and 14 studies in the MAs. The MAs revealed higher pNKCs among nonpregnant women with RM compared to controls (MD, 7.99 95 %CI 6.40-9.58; p < 0.00001). pNKCs were also higher in pregnant women with RM than in pregnant controls (MD, 8.21 95 %CI 6.08-10.34; p < 0.00001). Women with RM showed significantly decreased pNKCs after the immunotherapy compared to before (MD, -8.20 95 %CI -10.20 - -6.19; p < 0, 00001). Additionally, there is an association between high pNKCs and the risk of pregnancy loss in women with RM. However, included studies showed substantial heterogeneities regarding the inclusion criteria of patients, techniques measuring pNKC, and types of immunotherapies. More studies are needed to evaluate the clinical efficiency of pNKCs in managing RM.

Pregnancy loss and the risk of rheumatoid arthritis in Chinese women: findings from the China Kadoorie biobank

Considering the female preponderance of rheumatoid arthritis (RA), and disease onset typically after the reproductive years, pregnancy and childbirth may play a role in the aetiology of the disease. Adverse outcomes of pregnancy have been found to precede the diagnosis of autoimmune diseases, including RA, but the evidence is scant and inconsistent. Therefore, we investigate whether pregnancy loss is associated with the risk of RA in Chinese women. Data from the China Kadoorie Biobank, conducted by the University of Oxford and the Chinese Centre for Disease Control and Prevention, of 299,629 Chinese women who had been pregnant were used. Multivariable logistic regression and stratified analyses were employed to analyse the association between types of pregnancy loss with the risk of RA. Pregnancy loss was significantly associated with increased risk of RA (OR 1.12, 95% CI 1.06–1.18), specifically, spontaneous (OR 1.11, 95% CI 1.03–1.20) and induced abortions (OR 1.11, 95% CI 1.06–1.17). There was no significant association between stillbirth and the risk of RA (OR 1.07, 95% CI 0.97–1.18). The risk of developing RA increases with the number of pregnancy losses: one loss confers an OR of 1.09 (95% CI 1.03–1.16), two an OR of 1.13 (95% CI 1.05–1.20), three or more an OR of 1.19 (95% CI 1.10–1.28) and OR of 1.06 (95% CI 1.03–1.08) for each additional. Spontaneous and induced abortions are associated with an increased risk of RA in Chinese women.

Tolerance to noninherited maternal antigens, reproductive microchimerism and regulatory T cell memory: 60 years after 'Evidence for actively acquired tolerance to Rh antigens'

Compulsory exposure to genetically foreign maternal tissue imprints in offspring sustained tolerance to noninherited maternal antigens (NIMA). Immunological tolerance to NIMA was first described by Dr. Ray D. Owen for women genetically negative for erythrocyte rhesus (Rh) antigen with reduced sensitization from developmental Rh exposure by their mothers. Extending this analysis to HLA haplotypes has uncovered the exciting potential for therapeutically exploiting NIMA-specific tolerance naturally engrained in mammalian reproduction for improved clinical outcomes after allogeneic transplantation. Herein, we summarize emerging scientific concepts stemming from tolerance to NIMA that includes postnatal maintenance of microchimeric maternal origin cells in offspring, expanded accumulation of immune suppressive regulatory T cells with NIMA-specificity, along with teleological benefits and immunological consequences of NIMA-specific tolerance conserved across mammalian species.

Cross-Generational Reproductive Fitness Enforced by Microchimeric Maternal Cells

Exposure to maternal tissue during in utero development imprints tolerance to immunologically foreign non-inherited maternal antigens (NIMA) that persists into adulthood. The biological advantage of this tolerance, conserved across mammalian species, remains unclear. Here, we show maternal cells that establish microchimerism in female offspring during development promote systemic accumulation of immune suppressive regulatory T cells (Tregs) with NIMA specificity. NIMA-specific Tregs expand during pregnancies sired by males expressing alloantigens with overlapping NIMA specificity, thereby averting fetal wastage triggered by prenatal infection and non-infectious disruptions of fetal tolerance. Therefore, exposure to NIMA selectively enhances reproductive success in second-generation females carrying embryos with overlapping paternally inherited antigens. These findings demonstrate that genetic fitness, canonically thought to be restricted to Mendelian inheritance, is enhanced in female placental mammals through vertically transferred maternal cells that promote conservation of NIMA and enforce cross-generational reproductive benefits.